1. Field of the Invention
This invention relates to solid electrolytic capacitors and more particularly to solid electrolytic capacitors having an anode constructed of a valve metal, an oxide layer positioned thereupon and serving as a dielectric, a semiconductive electrolyte as a cathode, a cathode contacting member, and terminals for the anode and cathode.
2. Description of the Prior Art
Solid electrolytic capacitors are known in the prior art wherein tantalum is used as a valve material as processed to become a center anode. By a forming process, an oxide layer functioning as a dielectric is produced upon the anode. Semiconductor manganese dioxide is principally used as a cathode. A contact means is applied on the manganese dioxide layer generally consisting of a graphite layer and a silver layer thereupon. The silver layer is connected to the cathode terminal by use of solder. In order to obtain a strong solder connection between the terminal element and the silver layer, a contact is established between the two parts prior to soldering.
The above described capacitors do not have a current limiting value when they are connected with incorrect polarity across low-ohmic voltage sources when voltage breakthrough occurs. The very high short-circuit current which may occur will heat the capacitor member to such an extent that central portions of the capacitor used as the anode begin to ignite. In the case of capacitors having a plastic casing, the casing may start to burn. If such capacitors are arranged on conductor plates, adjacent components may also be destroyed by the intense heat. Furthermore, the danger exists that the entire conductor plate or printed circuit board may begin to burn and the device becomes destroyed.